The present invention is directed to a method and apparatus of introducing additives to a material used to form a composite panel, and, more particularly, to a method and apparatus of introducing additives, without the use of a blender, to a material used to form a composite panel.
Composite panels are typically formed of a raw material that is mixed with a binder. The mixture proceeds to a forming station that produces a mat of material, which is then subjected to heat and pressure in a hot pressing process to form the panel. Exemplary composite panels include oriented strand board (OSB), medium density fiberboard (MDF), wafer board, and particle board.
In a typical manufacturing process for a composite panel, a binder is added to the raw material by mechanical action in a large rotating drum, or blender. Other additives may also be introduced via the blender, either in liquid or powdered form, such as dry catalysts, fire retardants and wax. A typical OSB blender is approximately 12 foot by 30 foot, and rotates at approximately 4-26 rpms. In the manufacture of OSB, for example, a powdered or liquid resin is added to wood flakes that are on the order of 0.025xe2x80x3 thick in such a blender. The resin acts as a xe2x80x9cspot weldxe2x80x9d between the wood flakes during the hot pressing process.
These rotary blenders spray or atomize liquid resin, as well as other liquid additives, into the blender at a rate dependent on the flow of raw material. Application rates in the manufacture of OSB, for example, are typically 2-4% resin solids to wood solids. Powdered resins and additives are blown or mechanically conveyed to the blender. In the case of powdered resin, the resin often falls off during conveying to the forming station.
U.S. Pat. No. 5,914,153 to Swink et al. discloses a blender formed of a tumbling drum for blending resin and wood flakes. Wood flakes are introduced into the tumbling drum. A spinning cup atomizes resin and disperses it into the drum in order to coat tumbling wood flakes.
Adding liquid resin by atomization or spraying in a blender is limiting in that the resin coverage is often inefficient and all the flakes are unevenly coated. In the case where powdered resin is added at a blender, the resin often falls off during conveying to the forming station. Thus, additional resin is required to achieve the required properties for the panel. This adds costs to the manufacturing process, and can negatively impact the properties of the composite panel.
It is an object of the present invention to provide a method and apparatus to introduce powdered additives at a forming station for a composite panel that reduces or wholly overcomes some or all of the difficulties inherent in prior known devices. Particular objects and advantages of the invention will be apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this field of technology, in view of the following disclosure of the invention and detailed description of preferred embodiments.
The principles of the invention may be used to advantage to provide a method and apparatus to introduce powdered additives at a forming station used in the manufacture of composite panels. By introducing the additives at the forming station, the need for a blender is eliminated. Further, a more uniform application of the additive, e.g., a binder such as a resin, to the raw material, e.g., wood flakes, can be achieved, as well as reducing the amount of additive required.
In accordance with a first aspect, a method of forming a composite panel includes the steps of supplying a material to a forming station, supplying a dry additive to the material at the forming station, producing a mat comprising the material and the additive, and applying heat and pressure to the mat to produce a composite panel.
In accordance with another aspect, a method of forming a composite panel includes the steps of supplying wood elements to a forming station, adding a dry binder to the wood elements at the forming station, producing a mat comprising the wood elements and the binder; and applying heat and pressure to the mat to form a composite panel.
In accordance with yet another aspect, an apparatus for forming a composite panel includes a reservoir of raw material and at least one forming station configured to form a mat of the raw material. A dry material dispensing assembly introduces an additive to the forming station, and a press applies heat and pressure to transform the mat into a panel.
In accordance with a further aspect, an apparatus for forming oriented strand board includes a reservoir of wood strands and at least one forming station to form a mat out of the wood strands. A plurality of doffing rolls are housed in each forming station and are configured to present a substantially uniform flow of the wood strands as the mat is formed. A dry material dispensing assembly introduces an additive at the doffing rolls. A conveying assembly transfers the mat to a press that includes a heat source and a pressure source configured to form a panel of oriented strand board from the mat.
From the foregoing disclosure, it will be readily apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this area of technology, that the present invention provides a significant advance. Preferred embodiments of the present invention can provide significant cost savings by reducing the capital equipment and materials required to form composite panels, as well as improving the performance characteristics of the composite panels. These and additional features and advantages of the invention disclosed here will be further understood from the following detailed disclosure of preferred embodiments.